1. Field of the Invention
The present invention relates to the field of flash memory and, more particularly, to a data access method capable of reducing the number of erasing to flash memory and a data patch and access device that utilizes the method.
2. Description of Related Art
Currently, the flash memory is in wide spread use to emulate a hard disk drive in embedded system application since flash memory can preserve the content thereof when the power is turned off. As shown in FIG. 9, the flash memory 911 and the hard disk emulator 912 constitute the emulation hard disk drive 91. As such, the application system can perform read and write operations to the flash memory just like to a hard disk drive, such that the existing file system can work on it.
The use of the emulation hard disk drive emulated by flash memory is restricted by the characteristic of the flash memory. That is, although the flash memory can be read/written multiple times, it is required to erase the memory area before writing data thereto. The memory erase operation is processed by a physical segment. The number of erasing to a segment is limited (about 100000 time). Because such a limitation to the flash memory, the lifetime of the emulation hard disk drive is also limited.
To extend the lifetime of the emulation hard disk drive emulated by flash memory, the prior art is to reduce the number of erasing by improving the segment callback strategy. The callback strategy is focused on the time period and frequency of the data in use to avoid taking back the data segment that will be invalid soon. However, this approach neglects that the file system will produce many duplication data. Thus, the performance is poor and needs to be improved. Therefore, there is a need to have a novel design to access flash memory that can mitigate and/or obviate the aforementioned problems.